9 Cenozoic Tectonics in Asia and North America: Linking Processes Across Scales (Posters)

This session invites research integrating geologic, geomorphic, and paleoclimate data to advance understanding on orogenesis, seismic hazards, and global change.

Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Growth and incision of Pleistocene transpressional foreburg anticlines from a burial luminescence and 10Be cosmogenic surface exposure ages of transverse fan and terrace surfaces, Zereg basin, western Mongolia

Paper number: 9-4
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

We use geomorphic markers in the Zereg basin, western Mongolia to document recent inversion of syn-orogenic growth strata in basins adjacent to uplifting transpressional forebergs of the Mongolian Altai. Transverse streams and their erosional and depositional markers incise the forebergs creating variably tilted alluvial fans and river terraces that record progressive crustal deformation. We develop an age model for the treads of six mapped geomorphic surfaces preserved across the Bumbat Nuruu foreberg in the northeastern part of the Zereg basin using a soil chronosequence supported by luminescence and pending terrestrial cosmogenic nuclide (TCN) numerical ages. Field soil characteristics show systematic changes in soil thickness, color, clay content, and calcium carbonate stage consistent with relative stratigraphic age and surface stability. 

Published (84.1 +/- 9.4 kyrs) and new luminescence ages of alluvial sediments (55.66 ± 6.27; 73.14 ± 7.76 kyrs) are consistent with stratigraphy and soil characteristics and constrain repeated cut-and-fill events associated with the Qt 4, 5 and 6 treads, respectively during MIS 4 and 5a.

These data indicate quasi-periodic intervals of terrace formation at ~10-20 ka intervals, elucidating the rate of foreberg incision during the late Quaternary. Profiles extracted from differential handheld GPS surveys and drone-based structure-from-motion imagery indicate progressive but unsteady tilting consistent with foreberg growth atop a thrust-cored hanging wall anticline. Linear fits to terrace-tread longitudinal profiles quantify this tilting, with gradients ranging from ~44 to 98 m/km that decrease systematically from the oldest surface (Qf2) to the youngest and least-deformed surface (Qf6). 

The dated geomorphic markers extend paleomagnetic and rock-magnetic cyclostratigraphic based age models for synorogenic growth strata used to determine the upward and outward growth of the Mongolian Altai from the Miocene through the Pleistocene. In addition, they supply a critical paleoseismic framework for seismic hazard analyses that guide the development of rapidly growing urban infrastructure in western Mongolia. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410530

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